1. Field of the Invention
The present invention relates to a brake hydraulic control device for use in a vehicle and, in particular, to a brake hydraulic control device for use in a vehicle which is able to control the brake hydraulic pressures of drive and driven wheel brakes respectively by drive wheel control valve means corresponding to the drive wheel brakes and driven wheel control valve means corresponding to the driven wheel brakes, and also which is capable of execution of anti-lock brake control (which is hereinafter referred to as ABS control) and traction control as well as behavior stabilization control in the vehicle take-a-turn operation.
2. Description of the Related Art
Conventionally, a brake pressure control device of the above-mentioned type is already known, for example, from Japanese Patent Unexamined Publication No. 9-221015 of Heisei and the like.
In the brake pressure control device for use in a vehicle that is disclosed in the above-cited Japanese Patent Unexamined Publication No. 9-221015 of Heisei, there are employed a main liquid passage cut-off valve and a bypass cut-off valve. In particular, the main liquid passage cut-off valve is interposed between the drive and driven wheel control valve means and a master cylinder, and the discharge ports of pumps are connected between the main liquid passage cut-off valve and the drive and driven wheel control valve means. The bypass cut-off valve is interposed between the master cylinder and a driven wheel brake, in particular, in a bypass passage which goes around the main liquid passage cut-off valve and driven wheel control valve means.
According to the above structure, while the main liquid passage cut-off valve is opened and the bypass cut-off valve is closed, the brake hydraulic pressures of the drive and driven wheel brakes are controlled by the drive and driven wheel control valve means, to thereby be able to execute the ABS control. And, while the main liquid passage cut-off valve and bypass cut-off valve are both closed, the pumps are operated and the brake hydraulic pressures of the drive wheel brakes are controlled by the drive wheel control valve means, so that the traction control under the non-brake operation condition can be executed. Further, while the main liquid passage cut-off valve and bypass cut-off valve are both closed, the pumps are operated and the brake hydraulic pressures of the drive and driven wheel brakes are controlled by the drive and driven wheel control valve means, so that the behavior stabilization control in the vehicle take-a-turn operation under the non-brake operation condition can be executed.
Also, when the brake operation is executed during execution of the traction control or during the behavior stabilization control in the vehicle take-a-turn operation, the brake pressures of the driven wheel are increased by opening the bypass cut-off valve, to thereby prevent the delayed act or effect of the brakes when such control is terminated, which allows the driver to carry out such braking operation that corresponds to the intention of the driver.
However, in the above-mentioned conventional brake pressure control device, in order to prevent the delayed action or effect of the brake at the time of termination of the control, there are necessary the main liquid passage cut-off valve, the bypass passage which goes around the main liquid passage cut-off valve and driven wheel control valve means and is provided between the master cylinder and a driven wheel brake, and the bypass cut-off valve disposed in the bypass passage. Therefore, the number of parts required in the brake pressure control device is increased and the configuration of a hydraulic circuit is complicated.